US20130071549A1 - Dryers For Removing Solvent From A Drug-Eluting Coating Applied To Medical Devices - Google Patents
Dryers For Removing Solvent From A Drug-Eluting Coating Applied To Medical Devices Download PDFInfo
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- US20130071549A1 US20130071549A1 US13/235,238 US201113235238A US2013071549A1 US 20130071549 A1 US20130071549 A1 US 20130071549A1 US 201113235238 A US201113235238 A US 201113235238A US 2013071549 A1 US2013071549 A1 US 2013071549A1
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- stent
- dryer
- housing
- drying
- drying chamber
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/06—Chambers, containers, or receptacles
- F26B25/066—Movable chambers, e.g. collapsible, demountable
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B9/00—Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards
- F26B9/003—Small self-contained devices, e.g. portable
Definitions
- the present invention relates to drug-eluting medical devices; more particularly, this invention relates to processes for controlling the interaction among polymer, drug and solvent, and the release rate of a drug for drug eluting medical devices.
- a coating may be applied by a spray coating process.
- a drug-polymer composition dissolved in a solvent is applied to the surface of a medical device using this method.
- the amount of drug-polymer to be applied has been expressed as a target coating weight, which corresponds to the weight of the coating after a substantial amount of the solvent is removed.
- a “drug release profile”, or “release profile” means the morphology, or characteristics of a drug-eluting matrix that delivers an expected therapeutic behavior after being placed within a body.
- a drug release profile, or release profile therefore informs one of such things as the predictability of the release rate, variation, if any, in the release rate over time or on a per unit area basis across a drug-eluting surface.
- a relatively high coating weight per spray cycle has been sought in the past, because this minimizes process time and increases throughput. Maintaining control over the amount or rate of solvent removal is, however, challenging unless an applied coating layer is relatively thin. If the applied layer is too thick the removal of the solvent becomes more difficult to control or predict. When the solvent is removed from a thick layer, therefore, the potential for undesired interaction among the solvent, polymer and drug, and related problems begin to impair the ability to retain control over the release profile.
- Process conditions can affect the desired morphology. For example, if there is excess residual solvent, i.e., solvent not removed between or after a spray cycle, the solvent can induce a plasticizing effect, which can significantly alter the release rate. Therefore, it can be critically important to have a process that produces a coating with consistent properties—crystallinity, % solvent residue, % moisture content, etc. If one or more of these parameters are not properly controlled, such that it varies over the thickness or across a surface of a drug-eluting device, then the release profile is affected. One or more of these considerations can be more critical for some drug-polymer-solvent formulations than for other formulations.
- a solvent e.g., surface tension, vapor pressure or boiling point, viscosity, and dielectric constant
- a solvent can, of course, be removed by applying a heated gas over the stent. However, this drying step must be carefully controlled in order to achieve the desired end result. A uniform and efficient heat transfer from the gas to the coating surface must also take place.
- the evaporation rate of a suitable solvent has an inverse relationship with the coating thickness (generally inversely proportional to the thickness) for a thin film coating.
- the resistance increases non-linearly as the coating thickness increases. As alluded to earlier, this non-linearity should be avoided.
- the coating thickness is not too high more uniformity and control can be achieved in removing the solvent.
- a more consistent drug release profile is obtained because there is the least drug-solvent-polymer interaction, solvent plasticizing and drug extraction rate. It is therefore desired to achieve more control over, not only the uniformity of properties across the coating thickness and along the length of the stent, but also the ability to remove solvent. This is because residual solvent on the drug eluting stent may induce adverse biological responses, compromise coating properties, induce drug degradation, and alter release profile.
- a release rate can be better controlled by applying many coats of a low percentage solution, e.g., 5% of the final coating weight, with a drying step between each spray cycle.
- a drying step between each spray cycle.
- 20 coats are needed to produce the target coating weight.
- an efficient in-process drying step is needed.
- US20110000427 proposes using an external heat nozzle design having a narrow opening producing a drying gas exiting from the dryer plenum at relatively high velocity.
- This arrangement requires precise alignment between the stent and heat nozzle for uniform drying.
- the design can introduce extensive and interfering mixing of outside air into the gas stream before contacting the stent or scaffold; this mixing of outside air is uncontrolled and causes variation in the temperature across the drying area.
- the high velocity gas causes the stent to oscillate, which can be problematic for longer-length stents, such as those intended for peripheral vessels.
- the invention proposes an in-process dryer for maximizing in-process drying efficiency and uniformity for improving the product quality (e.g. coating and its drug release consistency).
- a dryer and associated process according to the invention can also obviate the need for an oven step which has been relied on to remove residual solvent, thereby streamlining the manufacturing process.
- a dryer nozzle according to the invention has a wider mouth or exit from the plenum than previously proposed stent dryer designs. With this design mean gas velocity at the dryer nozzle is reduced over earlier dryer designs, so that there is less or no influence by the surrounding ambient air and less oscillations of the stent during drying.
- the dryer is constructed as a telescoping dryer assembly, although other designs are contemplated, e.g., a dryer nozzle that is moved into and out of position as a single unit connected to a flexible gas supply.
- a shield surrounds the drying region, or drying chamber to isolate heated gas from surrounding cooler ambient air.
- the stent or scaffold
- the dryer nozzle is retractable, which allows clearance for movement of the sent or scaffold between spraying and drying stations. The feature of a retractable dryer nozzle also simplifies drying operations, such as concerns aligning the stent with the mouth or exit.
- a dryer according to the invention addresses alignment issues and uneven drying seen in prior designs by ensuring full coverage and uniform heat application.
- the influence of ambient air in the drying operation is effectively minimized or eliminated.
- Tests have shown that the temperature within the shielded area of the drying chamber and just above it is at a constant temperature, indicating that no ambient air is drawn into the drying chamber. Since the hot air within the drying chamber is at a slightly higher pressure than the surrounding ambient air, ambient air is prevented from being drawn into the drying chamber.
- the dryer nozzle includes internal diffusers, e.g., stacked spacer and screen assemblies, to uniformly mix the heated drying gas, resulting in a temperature uniformity of within 1 degree C. across the stent drying area.
- an inter-pass dryer that is used in a stent coating process improves on the art by providing an apparatus and method for forming a drug-eluting coating that offers greater control over the release rate for a drug and less undesired interaction between residual solvent and the drug-polymer matrix in the coating.
- inter-pass drying means drying, or removing solvent between one, two, three or more spray passes.
- the weight of material per coat is in some embodiments are very light, about 5% of the total coating weight according to one embodiment. This means, for this particular embodiment, 20 coats are needed to reach 100% of the coating weight.
- the invention provides one or more of the following additional improvements over the art.
- a method for applying a composition to a stent comprising the steps of spraying the composition on the stent; and drying the stent, including the steps of moving a drying chamber over the stent, applying a drying gas to dry the stent, and after drying the stent, moving the drying chamber away from the stent.
- a dryer nozzle for drying a stent includes a first housing configured for being connected to a gas supply; a second housing movable within the first housing, the second housing including a drying chamber in fluid communication with a mouth of the dryer nozzle and configured to receive and support a mandrel, the mouth being located at a base of the drying chamber, and a diffusion chamber disposed below the mouth.
- a stent coating system includes a sprayer; a telescoping dryer nozzle; and a linear actuator for moving a stent-supporting mandrel between the telescoping dryer nozzle and the sprayer.
- the system may further include a rotary actuator for rotating the stent-supporting mandrel to improve consistency and uniformity of solvent removal.
- FIG. 1A is side view of a dryer assembly in a first, retracted position according to one aspect of the disclosure.
- FIG. 1B is side view of the dryer assembly in a second, expanded position according to another aspect of the disclosure.
- FIG. 2 summarizes a process for coating a stent including a spraying step and in-process drying step using the dryer assembly of FIG. 1 .
- FIG. 3 is a rear perspective view of the dryer assembly.
- FIG. 4 is a front perspective, exploded assembly view of the dryer assembly showing component parts according to a preferred embodiment.
- FIG. 5 is a perspective view of a base cap of the dryer assembly of FIG. 4 .
- FIG. 6 is a perspective view of a diffuser housing of the dryer assembly of FIG. 4 .
- FIGS. 7A and 7B are perspective views of left and right grippers of a mandrel gripper of the dryer assembly of FIG. 4 .
- FIG. 8 is a perspective view of a base housing of the dryer assembly of FIG. 4 .
- FIG. 9 is a schematic of a control system that may be used with the dryer assembly to minimize transient flow or wait time and conserve dryer resources while a coating is being applied to a stent.
- a sprayer and dryer nozzle is used to form a drug-eluting coat on a surface of a stent.
- a stent is an intravascular prosthesis that is delivered and implanted within a patient's vasculature or other bodily cavities and lumens by a balloon catheter for balloon expandable stents and by a catheter with an outer stent restraining sheath for self expanding stents.
- the structure of a stent is typically composed of scaffolding, substrate, or base material that includes a pattern or network of interconnecting structural elements often referred to in the art as struts or bar arms.
- a stent typically has a plurality of cylindrical elements having a radial stiffness and struts connecting the cylindrical elements. Lengthwise the stent is supported mostly by only the flexural rigidity of slender-beam-like linking elements, which give the stent longitudinal flexibility. Examples of the structure and surface topology of medical devices such as a stent and catheter are disclosed by U.S. Pat. Nos. 4,733,665, 4,800,882, 4,886,062, 5,514,154, 5,569,295, and 5,507,768.
- one aspect of the stent coating process that has been simplified, or improved, as a result of the dryer according to the disclosure, is the ability to predict more consistently the rate of solvent removal and variation of that rate over the length of the stent.
- Increasing the predictability of a solvent's presence in the applied coating, or remaining when determining a final weight can greatly increase the ability and/or efficiency in which a predictable release rate for a drug can be provided in a medical device, in the form of an applied coating.
- the disclosure provides examples of spraying/drying components suited for addressing the previously discussed drawbacks and limitations in the art pertaining to a drug-eluting coating applied via a drug-polymer dissolved in a solvent.
- FIGS. 1A-1B show side views of a telescoping dryer 10 (dryer 10 ) according to one aspect of the disclosure.
- FIG. 2 shows a flow process for applying, via a spray apparatus, a composition, i.e., drug-polymer coating dissolved in a solvent, to a stent including applying one or more coats of the sprayed composition followed by a drying step that may include using dryer 10 .
- the dryer 10 may be included as a component to a stent coating apparatus.
- Such a stent coating apparatus implementing the process of FIG.
- a sprayer for placing the stent between a spraying area or chamber and a drying area for performing a drying step, or solvent removal step, between each of several coatings of composition sprayed onto the stent.
- a stent coating apparatus that may adopt principles of the disclosure are described in U.S. patent application Ser. Nos. 12/497,133; 12/027,947 and 11/764,006.
- the dryer(s) described therein may instead utilize a dryer according to the disclosure, as will be understood.
- the stent (supported on a mandrel 15 ) is moved into position over the dryer 10 , as indicated in FIG. 1A .
- Mandrel grippers 60 then engage a distal end 15 a of the mandrel 15 to account for any slight misalignments of the stent position over the dryer exit or mouth and stabilize the stent as it rotates and is impacted by gas exiting from the dryer plenum.
- a diffuser housing 30 telescopes or deploys from a base housing 20 (using a linear actuator mechanism 50 ) to place or enclose the stent within a drying chamber 32 , as indicated in FIG. 1B .
- the diffuser housing 30 retracts back into the base housing 20 , the grippers 60 are released from the mandrel end 15 a and the stent moved back to the spraying station to apply the next coating.
- FIGS. 1A and 1B show the stent positioned above the dryer 10 .
- the stent may alternatively be located below the dryer 10 .
- the drying chamber 32 would be placed above the stent and the drying gas directed downward, rather than placed below the stent and directed upward, respectively, as depicted in these drawings.
- the stent, supported on the mandrel 15 is rotated by a rotary mechanism (not shown) coupled to the mandrel 15 as the sprayer applies a drug-polymer dissolved in a solvent, e.g., DMAc or Acetone, to the surface of the stent.
- a solvent e.g., DMAc or Acetone
- This rotary mechanism is also used to rotate the stent while it is disposed within the drying chamber 32 to facilitate uniform removal of solvent about the circumference of the stent during drying.
- a mass of heated gas exits from the mouth of the dryer (at a base of the drying chamber 32 ) to accelerate the evaporation, or boiling-off of solvent from the coated stent surface.
- this sprayer-dryer coating process is repeated until a final coating weight of drug-polymer and remaining solvent is measured.
- the gas is capable of producing a uniform heat transfer across the surface of stents or scaffolds, even for stents or scaffolds having lengths of 100 mm, 150 mm, and 200 mm.
- a coating process according to FIG. 2 may be preprogrammed, or programmed on the fly to adjust parameters such as number of coats, or passes with the sprayer between drying steps, number of cycles of spraying and drying, etc. These and related parameters may be governed by the polymer-drug or solvent used, type of stent or medical device being coated, e.g., surface geometry.
- the protocol for coating a stent may be governed by a predetermined number of coating cycles, i.e., spraying then drying, based on an analytically determined final coating weight, or by intermittent weighing of the stent to determine the number of cycles needed to arrive at the target coating weight.
- FIGS. 3 and 4 show an assembled rear perspective view and exploded front perspective assembly view, respectively, of the dryer 10 .
- a mouth or exit of the dryer 10 is present at the base of the drying chamber 32 and has dimensions the same as the opening to the drying chamber 32 ; in other words, the walls forming the drying chamber 32 are parallel to each other or the cross-sectional area of the entrance to the drying chamber 32 is the same as the cross-sectional area of the opening through which the stent passes when entering/exiting the drying chamber 32 .
- a gas supply is connected to an entrance of the dryer 10 provided by the base housing 20 .
- the drying gas e.g., heated nitrogen or air, is supplied through a gas supply 2 b connected to a heater assembly 2 .
- the heater assembly 2 includes a tubular conduit with heating coils exposed to the gas stream as it travels towards the dryer entrance 9 .
- the coils are connected to a power source via a power connection.
- a plenum of the dryer 10 is formed by internal volumes of the base housing 20 , the diffuser housing 30 and a base cap 70 .
- Perspective views of the base cap 70 and diffuser housing 30 are illustrated in FIGS. 5 and 6 , respectively.
- a hole in the dryer base housing 20 (hidden from view) is formed to co-align with a similar shaped hole in the base cap 70 (also hidden from view) to provide a passage for gas into the interior of the base cap 70 .
- the hole or passage for gas through the base housing 20 includes a threading to sealingly engage a complimentary threaded fitting 2 c of the heated gas supply.
- Gas entering through this passage passes directly into the interior of the base cap 70 , exits through a hole 72 formed at the top of the base cap 70 then passes up through the diffuser housing 30 .
- the base cap 70 and diffuser housing 30 are contained within the base housing 20 when fully assembled.
- one or more mixing regions are provided within the diffuser housing 30 so that the gas entering the drying chamber 32 has a more uniform heat transfer across the length of the stent.
- Preferably three mixing regions are used for dryer 10 .
- Each mixing region is formed by a diffuser screen 42 and spacer 40 .
- Each screen and spacer are stacked on top of each other, as indicated in FIG. 4 . From tests it was found that three spacers and screen assemblies were sufficient to cause no more than about a 1 degree Celsius temperature difference within the drying chamber 32 during a drying step.
- FIG. 4 indicates the order of assembly of the portions forming the plenum of the dryer 10 , i.e., diffuser housing 30 , base cap 70 , base housing 20 and spacers and screens 40 , 42 .
- the three spacers and screens 40 , 42 are placed inserted within the diffuser housing 30 and may be held in place by pins at the edge 31 .
- the diffuser housing 30 is placed within the dryer base 20 through a bottom edge 24 thereof.
- the dryer housing 20 and diffuser housing 30 are then placed on the base cap 70 such that a lower edge 24 of the dryer housing 20 rests on a lower flange 76 of the base cap 70 .
- the lower spacer 40 a rests on an upper surface 74 of the base cap 70 .
- the base housing 20 is press-fit onto the base cap 70 to provide a fluid-tight seal between the walls of the two structures.
- This assembled configuration of the dryer 10 is depicted in FIG. 1A .
- gas travels from the gas supply into the interior of the base cap 70 , though the exit hole 72 and then through the diffuser housing 30 .
- the diffuser housing 30 is lifted up to position the stent within the drying chamber 32 ( FIG. 1B )
- the spacer 40 a lifts off the surface 74 of the base cap 70 .
- a tight but slidable fit is formed between the interior walls of the housing 20 and a lower flange 31 of the diffuser housing 30 .
- this fit maintains a desired gas pressure within the plenum while the dryer 10 is expanded (or housing 30 lifted) to receive the stent in the drying chamber 32 , and while allowing the diffuser housing 30 to be moved up and down by the actuator 50 while the housing 20 and base cap 70 remain stationary ( FIG. 1B ).
- the travel upwards of the diffuser housing 30 within the base housing 20 is limited by the flange 31 .
- the flange 31 abuts an upper surface of the opening 22 of the diffuser housing 20 , thereby preventing further upward movement.
- the edge 31 slides against along the walls of the housing 20 as the diffuser housing 30 is being moved upwards and downwards within the housing 20 by the actuator 50 . More generally, the sliding fit between these telescoping parts enables a plenum pressure to be achieved and maintained (no leaks) while the dryer 10 is retracted/shortened and expanded/lengthened.
- the aforementioned structure, i.e., housings 20 , 30 and base cap 70 , and mechanism 50 that form the plenum for the dryer 10 may be thought of as a telescoping dryer.
- the diffuser housing 30 Prior to the stent being positioned over the drying chamber 32 , the diffuser housing 30 is retracted within the base housing 20 to provide clearance for the stent and mandrel 15 to be linear displaced from the spray station to a position over the drying chamber 32 .
- the dryer plenum is then essentially elongated or expanded to bring the stent into the drying chamber 32 of the diffuser housing 30 .
- a “telescoping dryer assembly” is intended to mean an arrangement of housings forming a plenum that slide inward and outward in overlapping fashion in a manner analogous to how a hand telescope slides inward and outward in an overlapping fashion, to thereby provide a variable length channel or internal passage for a pressurized fluid to pass through, i.e., a variable length plenum.
- the dryer 10 components and actuating mechanisms 55 and 50 are secured to a plate 14 , which is connected to a pair of blocks 16 and brackets 12 .
- the actuating mechanism 55 is used to displace left and right grippers 62 , 64 towards and away from each other to grip and release, respectively, the distal end 15 a of the mandrel 15 ; this movement being indicated by the left and right arrows G in FIG. 3 .
- a detailed view of each gripper 62 , 64 is shown in FIGS. 7A-7B .
- the actuating mechanism 50 (e.g., one or more hydraulic actuators, such as air cylinders, operated as part of a servomechanism pre-programmed or controlled by a computer processor to produce the desired movement in the housing 30 in accordance with a drying/spraying process as shown in FIG. 2 ) is used to raise and lower the diffuser housing 30 ; this movement indicated by the up and down arrows L in FIG. 3 .
- a connecting plate 54 has a rim, which is placed over the diffusing housing and secured to a top ledge 34 of the diffuser housing 30 , and a flange 54 a that is secured to a platform 54 b that is movable up and down by a pair of air cylinders 56 a , 56 b .
- FIG. 3 shows the dryer 10 configuration with the housing 30 raised to position the stent within the drying chamber 32 and the gripper pair 62 , 64 gripping the end 15 a of the mandrel 15 . This is also the configuration shown in FIG. 1B .
- FIG. 5 shows a perspective view of the base cap 70 , with the portions identified as previously described.
- the dryer 10 preferably has an elongate shape with rounded ends, just as the drying chamber 32 is shaped to receive the stent or scaffold.
- the base cap 70 may be formed to have walls that are thicker than the housings 20 , 30 (see FIG. 1A ) to provide increased insulation capability. Since the gas enters here and is redirected 90 degrees to exit from hole 72 , there is a greater heat loss possibility than after the gas exits through hole 72 . As such, the walls are made thicker and preferably they are made from PEEK.
- a last step of the assembly for dryer 10 is to press fit the housing 20 (with diffuser housing 30 inside) onto the base cap 70 . This last step essentially seals the dyer 10 and forms the interior space for the dryer plenum.
- FIG. 6 shows a perspective view of the diffuser housing 30 , with features of this structure as previously described.
- the drying chamber 32 is elongate with rounded ends to receive the stent or scaffold therein.
- the drying chamber 32 provides a surrounding shield or walls 30 b that rise up from the ledge 34 , which ledge 34 locates the exit opening from the plenum (the dryer mouth) into the drying chamber 32 , thereby also reflecting a depth of the drying chamber 32 .
- Gas flowing near the stent and within the drying chamber 32 may exit from the plenum at a relatively low velocity which favorably limits the amount of regress or interference from ambient air.
- FIGS. 7A and 7B show perspective views of grippers 62 , 64 , respectively.
- Each has arms 58 a , 58 b that form holes 57 a , 57 a at lower ends thereof to secure the grippers 62 , 64 to the actuator mechanism 55 ( FIG. 4 ) using bolts.
- the actuator mechanism 55 e.g., one or more hydraulic actuators, such as air cylinders, operated as part of a servomechanism pre-programmed or controlled by a computer processor to produce the desired movement in the grippers in accordance with a drying/spraying process as shown in FIG. 2 ).
- V-shaped sections 66 , 67 aligned with slots 63 a , 63 b , function as guiding surfaces to urge the mandrel 15 into the semicircular slots 63 a , 63 b (see FIGS. 1B and 3 ).
- FIGS. 1B and 3 see FIGS. 1B and 3 .
- the V-shaped section 67 is disposed within the space 69 of the gripper 62 when the mandrel end 15 a is engaged by the grippers 62 , 64 .
- the grippers 62 , 64 come together. Any misalignment of the mandrel end 15 a is adjusted by the V-shaped sections engaging the mandrel end 15 a and urging it towards alignment with the slots 63 a , 63 b .
- the grippers 62 , 64 are moved into contact with each other, the mandrel end 15 a is held in place within the circular passage formed by the slots 63 a , 63 b .
- the mandrel end 15 a may rotate while it is disposed within the circular passage formed by the slots 63 a , 63 b.
- the shield 30 b forming the drying chamber 32 includes a first notch 36 disposed at one rounded end, and a second notch 38 disposed at a second or opposed rounded end. These notches 36 , 38 are used to allow the mandrel that the stent sits on to lower the stent to within the drying chamber 32 during the drying.
- the stent will oscillate since it rotates which presents a varying surface area to the gas exiting (in addition to the non-laminar or transient flow in and around the stent).
- the problem of oscillations is especially noted for stents that are 40 mm and longer, e.g., stents (or scaffolds) intended for the superficial femoral artery.
- the dryer 10 includes a support for the mandrel 15 distal end 15 a , i.e., mandrel grippers 60 , in addition to the notches 36 , 38 .
- mandrel grippers 60 With the additional support provided by grippers 60 the stent becomes effectively fixed-supported at the mandrel distal end 15 a when disposed over the dryer mouth (exit of the plenum), yet is still capable of being rotated about the mandrel axis by a rotary mechanism coupled to the mandrel.
- This support may be achieved without interference with drying and prevents contact between the stent/scaffold and the walls 30 b or mandrel 15 as the gas passes over the stent/scaffold.
- the stent is mounted onto the mandrel 15 prior to the start of the stent coating process ( FIG. 2 ).
- the mandrel 15 controls the stent position during drying and spraying.
- the mandrel 15 generally maintains axial alignment of the stent, and causes the stent to rotate at generally the same rate as the mandrel 15 , which has a proximal end that fits into a chuck.
- the chuck delivers a torque to the mandrel 15 .
- the slots 36 and 38 provide a sufficient clearance to allow the mandrel 15 to rotate.
- the mated grooves 63 a , 63 b ( FIGS. 7A-7B ) also provide this clearance for rotation. Some heating gas will escape through the slots 36 and 38 .
- FIG. 8 shows a perspective view of the base housing 20 , with the portions identified as previously described.
- the base housing 20 includes a threaded fitting (hidden from view) that receives the fitting for the gas supply.
- the diffuser housing 30 and spacers/screens 40 , 42 are received in the base housing 20 .
- the walls forming the drying chamber 32 extend out from the opening 22 of the base housing 20 (see FIG. 1B ).
- an oven step for removing residual solvent from the stent or scaffold.
- the oven step may be skipped as tests show that the dryer 10 and process as shown and described may remove solvent at a sufficient rate during the process of FIG. 2 to obviate an oven step. This is desirable as it reduces manufacturing time for the medical device.
- the residual acetone data for the two groups are listed in the TABLE 1.
- the data shows that there is not much different between the average of the residual acetone level between the two groups (between 1 to 2 micrograms). This is because the actual amount of a residual solvent present in a coated stent can vary within a few micro-grams of a measured amount, which is what TABLE 1 shows. Moreover, in some applications up to 5 ⁇ g of residual solvent remaining in the coating is considered acceptable. Accordingly, the test suggests there may be no need to have an oven bake step when using a dryer constructed in accordance with dryer 10 .
- a gas flow rate through the heater assembly 2 in FIG. 1 may be monitored/controlled by a commercially available mass flow regulator (not shown).
- a mass flow regulator may be used to operate an adjustable valve coupling the gas supply line 2 b to a gas source to produce the desired flow rate.
- a suitable mass flow regulator is the Aalborg GFCS series programmable mass flow regulator.
- the dryer is not in use when the stent is being coated. If the dryer is shut down or the flow rate reduced the temperature of the gas at the entrance to the plenum 10 of the dryer 1 will decrease. If the stent is moved into position above the nozzle mouth for drying and the valve opened to increase the flow rate, there will be a period of transient flow. It is desirable to avoid a period of solvent removal by transient gas flow, since the rate or amount of solvent removal by transient flow can be difficult to predict. It is preferred, therefore, that the stent is dried only during steady state flow conditions.
- gas flow at the dryer is instead maintained at a constant rate, then the temperature may be maintained. However, this wastes gas resources. It would be desirable if the gas flow rate could be reduced when the dryer is not in use while holding the gas temperature at a constant value.
- a closed loop control is preferably implemented with a stent dryer system according to the disclosure, so that the gas temperature may be maintained at variable flow rates.
- FIG. 9 a schematic of this closed-loop control is illustrated.
- a controller 300 continuously receives input temperatures at the entrance of the plenum from a thermocouple 302 and the gas flow rate upstream of the plenum entrance from a flow sensor 304 .
- the controller 300 may be programmed to reduce the gas flow rate when the dryer is not in use, and increase the gas flow rate when the stent is ready to be moved into position above the dryer mouth.
- a dryer system may be operated at variable flow rates during a coating process while maintaining a substantially steady state gas flow during the drying stage, or a minimal period of transient flow conditions until a steady state condition is reached. This improves/maintains the predictability of solvent removal during drying, minimizes down time and allows gas resources to be conserved.
- the coated stent is almost immediately subject to the drying step and dried in a manner that allows the improved prediction of solvent removal. As discussed earlier, this is a critical step in the process of producing a predictable release rate for a drug-eluting stent and accurate assessment of whether the desired drug-polymer coating weight has been reached.
- the controller 300 After, or just prior to completion of an application of coating composition on the stent, the controller 300 increases the gas flow temperature to the drying gas flow rate. While the gas flow is being increased, the controller 300 monitors the temperature at the plenum entrance 2 c by input received from the thermocouple 302 and the power increased to the heating coils as necessary to maintain the temperature of the exiting gas flow. Once the gas flow has reached the operating flow rate and temperature, the stent is moved into position above the drying chamber 32 and the housing 30 raised. The stent is rotated. After drying is complete, the gas flow is again returned to the idle state and the power to the heating coils decreased as necessary to maintain the same gas flow temperature (based on input received from the thermocouple 302 ) at/near location 2 c . The process repeats until the desired coating weight is obtained.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to drug-eluting medical devices; more particularly, this invention relates to processes for controlling the interaction among polymer, drug and solvent, and the release rate of a drug for drug eluting medical devices.
- 2. Background of the Invention
- Strict pharmacological and good mechanical integrity of a drug eluting medical device are required to assure a controlled drug release. Significant technical challenges exist when developing an effective and versatile coating for a drug eluting medical device, such as a stent.
- A coating may be applied by a spray coating process. A drug-polymer composition dissolved in a solvent is applied to the surface of a medical device using this method. The amount of drug-polymer to be applied has been expressed as a target coating weight, which corresponds to the weight of the coating after a substantial amount of the solvent is removed.
- Previous efforts to produce a more consistent and stable drug release profile have been met with challenges. Prior efforts have focused on the type or structure of the polymer carrier for a drug, and the type of solvent used. However, these improvements have not been able to satisfactorily meet the needs for certain clinical applications, or provide a morphology that can be widely used.
- A “drug release profile”, or “release profile” means the morphology, or characteristics of a drug-eluting matrix that delivers an expected therapeutic behavior after being placed within a body. A drug release profile, or release profile therefore informs one of such things as the predictability of the release rate, variation, if any, in the release rate over time or on a per unit area basis across a drug-eluting surface.
- It has been previously discovered that a significant improvement in the ability to tailor a drug release profile to suit a particular objective such as producing a specific release rate, uniformity in the release rate over a drug eluting surface, and/or uniformity in a production setting (high throughput) lay in obtaining more precise control over the amount of solvent present, or rate of solvent removal. The criticality of solvent removal, distribution, etc. generally depends on the drug-polymer-solvent formulation and particular objectives. While it was already known that the morphology of a drug-polymer matrix is influenced by the presence of a solvent, it was later discovered that this interaction played a more significant role than previously thought. Based on this conclusion, a more effective process for controlling the amount of solvent-polymer-drug interaction was sought. It was found that the coating weight per spray cycle and manner in which solvent was removed, in connection with the coating thickness was an important consideration.
- A relatively high coating weight per spray cycle has been sought in the past, because this minimizes process time and increases throughput. Maintaining control over the amount or rate of solvent removal is, however, challenging unless an applied coating layer is relatively thin. If the applied layer is too thick the removal of the solvent becomes more difficult to control or predict. When the solvent is removed from a thick layer, therefore, the potential for undesired interaction among the solvent, polymer and drug, and related problems begin to impair the ability to retain control over the release profile.
- Process conditions can affect the desired morphology. For example, if there is excess residual solvent, i.e., solvent not removed between or after a spray cycle, the solvent can induce a plasticizing effect, which can significantly alter the release rate. Therefore, it can be critically important to have a process that produces a coating with consistent properties—crystallinity, % solvent residue, % moisture content, etc. If one or more of these parameters are not properly controlled, such that it varies over the thickness or across a surface of a drug-eluting device, then the release profile is affected. One or more of these considerations can be more critical for some drug-polymer-solvent formulations than for other formulations.
- To facilitate the incorporation of a drug on a stent, spraying a low solid percent polymer/drug solution over the stent followed by removing the solvent has become feasible in controlling the amount of drug (in micrograms range) deposited on the stent and the release profile. A good coating quality benefits from using this spray technique, i.e., properties such as the crystallinity, % solvent residue, and % moisture content are more controllable as the coating weight is built up over several applied coatings.
- Previous studies of the drying effect on drug release indicated a need for an optimal in-process or inter-pass drying technique to remove a solvent on the coated stent after each spray cycle. This is a critical step in producing more stable products while retaining a high throughput.
- The properties of a solvent, e.g., surface tension, vapor pressure or boiling point, viscosity, and dielectric constant, used in dissolving a polymer have a dominant effect on the coating quality, coating process throughput, drug stability, and the equipment required to process it. A solvent can, of course, be removed by applying a heated gas over the stent. However, this drying step must be carefully controlled in order to achieve the desired end result. A uniform and efficient heat transfer from the gas to the coating surface must also take place.
- The evaporation rate of a suitable solvent has an inverse relationship with the coating thickness (generally inversely proportional to the thickness) for a thin film coating. And the resistance increases non-linearly as the coating thickness increases. As alluded to earlier, this non-linearity should be avoided. When the coating thickness is not too high more uniformity and control can be achieved in removing the solvent. As a result, a more consistent drug release profile is obtained because there is the least drug-solvent-polymer interaction, solvent plasticizing and drug extraction rate. It is therefore desired to achieve more control over, not only the uniformity of properties across the coating thickness and along the length of the stent, but also the ability to remove solvent. This is because residual solvent on the drug eluting stent may induce adverse biological responses, compromise coating properties, induce drug degradation, and alter release profile.
- Thus, it has been determined that a release rate can be better controlled by applying many coats of a low percentage solution, e.g., 5% of the final coating weight, with a drying step between each spray cycle. Thus, in this example 20 coats are needed to produce the target coating weight. In order to make this coating process more feasible as a production-level method, while maintaining control over the solvent and solvent-drug-polymer interaction, as just discussed, an efficient in-process drying step is needed.
- Effective ways to remove residual solvent in the applied coating becomes more important for coating formulations that are more sensitive to a residual solvent level. As explained above, excessive remaining solvent impacts the coating morphology and property. For example, in the case of a coating formulation used for a polymer scaffold, e.g., PLLA, residual solvent left in the coating can induce phase separation between the drug and polymer because the drug and polymer are not miscible. This can cause variation of the drug release rate and adversely impact the physical properties of the coating. It is therefore desirable to achieve an optimized in-process dry nozzle design to ensure the removal of most of the residual solvent between successive spray cycles. Examples of dryers seeking to achieve this objective are described in US20110059228 and US20110000427.
- For example, US20110000427 proposes using an external heat nozzle design having a narrow opening producing a drying gas exiting from the dryer plenum at relatively high velocity. This arrangement requires precise alignment between the stent and heat nozzle for uniform drying. The design can introduce extensive and interfering mixing of outside air into the gas stream before contacting the stent or scaffold; this mixing of outside air is uncontrolled and causes variation in the temperature across the drying area. Additionally, the high velocity gas causes the stent to oscillate, which can be problematic for longer-length stents, such as those intended for peripheral vessels.
- There is a continuing need for obtaining a better control over the drug-eluting product. Specifically, there is a need to develop an inter-pass drying process that is better able to remove solvent to achieve improved rate of release of a drug, uniformity of release rate over the stent length and/or the effectiveness of a drug when released from the coating. It is also desirable to reduce processing time when applying a drug-eluting coating.
- The invention proposes an in-process dryer for maximizing in-process drying efficiency and uniformity for improving the product quality (e.g. coating and its drug release consistency). A dryer and associated process according to the invention can also obviate the need for an oven step which has been relied on to remove residual solvent, thereby streamlining the manufacturing process.
- A dryer nozzle according to the invention has a wider mouth or exit from the plenum than previously proposed stent dryer designs. With this design mean gas velocity at the dryer nozzle is reduced over earlier dryer designs, so that there is less or no influence by the surrounding ambient air and less oscillations of the stent during drying. In a preferred embodiment the dryer is constructed as a telescoping dryer assembly, although other designs are contemplated, e.g., a dryer nozzle that is moved into and out of position as a single unit connected to a flexible gas supply. A shield surrounds the drying region, or drying chamber to isolate heated gas from surrounding cooler ambient air. The stent (or scaffold) is disposed within this drying chamber during the drying step. The dryer nozzle is retractable, which allows clearance for movement of the sent or scaffold between spraying and drying stations. The feature of a retractable dryer nozzle also simplifies drying operations, such as concerns aligning the stent with the mouth or exit.
- A dryer according to the invention addresses alignment issues and uneven drying seen in prior designs by ensuring full coverage and uniform heat application. In addition, the influence of ambient air in the drying operation is effectively minimized or eliminated. Tests have shown that the temperature within the shielded area of the drying chamber and just above it is at a constant temperature, indicating that no ambient air is drawn into the drying chamber. Since the hot air within the drying chamber is at a slightly higher pressure than the surrounding ambient air, ambient air is prevented from being drawn into the drying chamber. The dryer nozzle includes internal diffusers, e.g., stacked spacer and screen assemblies, to uniformly mix the heated drying gas, resulting in a temperature uniformity of within 1 degree C. across the stent drying area.
- Accordingly, an inter-pass dryer, according to the invention, that is used in a stent coating process improves on the art by providing an apparatus and method for forming a drug-eluting coating that offers greater control over the release rate for a drug and less undesired interaction between residual solvent and the drug-polymer matrix in the coating. The term “inter-pass drying” means drying, or removing solvent between one, two, three or more spray passes. The weight of material per coat is in some embodiments are very light, about 5% of the total coating weight according to one embodiment. This means, for this particular embodiment, 20 coats are needed to reach 100% of the coating weight.
- In view of the foregoing, the invention provides one or more of the following additional improvements over the art.
- According to one aspect of invention, a method for applying a composition to a stent, comprising the steps of spraying the composition on the stent; and drying the stent, including the steps of moving a drying chamber over the stent, applying a drying gas to dry the stent, and after drying the stent, moving the drying chamber away from the stent.
- According to another aspect of invention, a dryer nozzle for drying a stent includes a first housing configured for being connected to a gas supply; a second housing movable within the first housing, the second housing including a drying chamber in fluid communication with a mouth of the dryer nozzle and configured to receive and support a mandrel, the mouth being located at a base of the drying chamber, and a diffusion chamber disposed below the mouth.
- According to another aspect of invention, a stent coating system includes a sprayer; a telescoping dryer nozzle; and a linear actuator for moving a stent-supporting mandrel between the telescoping dryer nozzle and the sprayer. The system may further include a rotary actuator for rotating the stent-supporting mandrel to improve consistency and uniformity of solvent removal.
- All publications and patent applications mentioned in the present specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. To the extent there are any inconsistent usages of words and/or phrases between an incorporated publication or patent and the present specification, these words and/or phrases will have a meaning that is consistent with the manner in which they are used in the present specification.
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FIG. 1A is side view of a dryer assembly in a first, retracted position according to one aspect of the disclosure. -
FIG. 1B is side view of the dryer assembly in a second, expanded position according to another aspect of the disclosure. -
FIG. 2 summarizes a process for coating a stent including a spraying step and in-process drying step using the dryer assembly ofFIG. 1 . -
FIG. 3 is a rear perspective view of the dryer assembly. -
FIG. 4 is a front perspective, exploded assembly view of the dryer assembly showing component parts according to a preferred embodiment. -
FIG. 5 is a perspective view of a base cap of the dryer assembly ofFIG. 4 . -
FIG. 6 is a perspective view of a diffuser housing of the dryer assembly ofFIG. 4 . -
FIGS. 7A and 7B are perspective views of left and right grippers of a mandrel gripper of the dryer assembly ofFIG. 4 . -
FIG. 8 is a perspective view of a base housing of the dryer assembly ofFIG. 4 . -
FIG. 9 is a schematic of a control system that may be used with the dryer assembly to minimize transient flow or wait time and conserve dryer resources while a coating is being applied to a stent. - According to a preferred implementation of the invention, a sprayer and dryer nozzle is used to form a drug-eluting coat on a surface of a stent. A stent is an intravascular prosthesis that is delivered and implanted within a patient's vasculature or other bodily cavities and lumens by a balloon catheter for balloon expandable stents and by a catheter with an outer stent restraining sheath for self expanding stents. The structure of a stent is typically composed of scaffolding, substrate, or base material that includes a pattern or network of interconnecting structural elements often referred to in the art as struts or bar arms. A stent typically has a plurality of cylindrical elements having a radial stiffness and struts connecting the cylindrical elements. Lengthwise the stent is supported mostly by only the flexural rigidity of slender-beam-like linking elements, which give the stent longitudinal flexibility. Examples of the structure and surface topology of medical devices such as a stent and catheter are disclosed by U.S. Pat. Nos. 4,733,665, 4,800,882, 4,886,062, 5,514,154, 5,569,295, and 5,507,768.
- As discussed earlier, one aspect of the stent coating process that has been simplified, or improved, as a result of the dryer according to the disclosure, is the ability to predict more consistently the rate of solvent removal and variation of that rate over the length of the stent. Increasing the predictability of a solvent's presence in the applied coating, or remaining when determining a final weight can greatly increase the ability and/or efficiency in which a predictable release rate for a drug can be provided in a medical device, in the form of an applied coating.
- Moreover, as the design or desired loading of polymer-drug on the stent is determined from the measured weight, it will be readily appreciated that there needs to be an accurate, reliable and repeatable process for being able to determine the amount and distribution of solvent remaining over the length of the stent. This is especially true when less volatile solvents are used, e.g., DMAc as opposed to the more volatile solvent Acetone. Since it is expected that a greater percentage of solvent will remain after drying for solvents having higher boiling points, the coating is more susceptible to variations in a solvent's presence over the stent surface and/or across the coating thickness. Also when drying a polymer Acetone mixture, the rate and uniformity of drying affects the % crystallinity and thus the amount of locked in residual solvent.
- The disclosure provides examples of spraying/drying components suited for addressing the previously discussed drawbacks and limitations in the art pertaining to a drug-eluting coating applied via a drug-polymer dissolved in a solvent.
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FIGS. 1A-1B show side views of a telescoping dryer 10 (dryer 10) according to one aspect of the disclosure.FIG. 2 shows a flow process for applying, via a spray apparatus, a composition, i.e., drug-polymer coating dissolved in a solvent, to a stent including applying one or more coats of the sprayed composition followed by a drying step that may include usingdryer 10. Accordingly, thedryer 10 may be included as a component to a stent coating apparatus. Such a stent coating apparatus implementing the process ofFIG. 2 includes a sprayer, thedryer 10 and actuators for placing the stent between a spraying area or chamber and a drying area for performing a drying step, or solvent removal step, between each of several coatings of composition sprayed onto the stent. Examples of a stent coating apparatus that may adopt principles of the disclosure are described in U.S. patent application Ser. Nos. 12/497,133; 12/027,947 and 11/764,006. In these examples, the dryer(s) described therein may instead utilize a dryer according to the disclosure, as will be understood. - Referring, briefly, to side views of the
dryer 10 as depicted inFIGS. 1A-1B , after one or more coatings are applied by a sprayer, the stent (supported on a mandrel 15) is moved into position over thedryer 10, as indicated inFIG. 1A . Mandrel grippers 60 then engage adistal end 15 a of themandrel 15 to account for any slight misalignments of the stent position over the dryer exit or mouth and stabilize the stent as it rotates and is impacted by gas exiting from the dryer plenum. Adiffuser housing 30 telescopes or deploys from a base housing 20 (using a linear actuator mechanism 50) to place or enclose the stent within a dryingchamber 32, as indicated inFIG. 1B . After the drying step is complete, thediffuser housing 30 retracts back into thebase housing 20, thegrippers 60 are released from the mandrel end 15 a and the stent moved back to the spraying station to apply the next coating. These steps of a stent coating process are summarized inFIG. 2 . -
FIGS. 1A and 1B show the stent positioned above thedryer 10. However, the stent may alternatively be located below thedryer 10. In such an arrangement, the dryingchamber 32 would be placed above the stent and the drying gas directed downward, rather than placed below the stent and directed upward, respectively, as depicted in these drawings. - The stent, supported on the
mandrel 15, is rotated by a rotary mechanism (not shown) coupled to themandrel 15 as the sprayer applies a drug-polymer dissolved in a solvent, e.g., DMAc or Acetone, to the surface of the stent. This rotary mechanism is also used to rotate the stent while it is disposed within the dryingchamber 32 to facilitate uniform removal of solvent about the circumference of the stent during drying. A mass of heated gas exits from the mouth of the dryer (at a base of the drying chamber 32) to accelerate the evaporation, or boiling-off of solvent from the coated stent surface. In a preferred embodiment, this sprayer-dryer coating process is repeated until a final coating weight of drug-polymer and remaining solvent is measured. During each drying stage the gas is capable of producing a uniform heat transfer across the surface of stents or scaffolds, even for stents or scaffolds having lengths of 100 mm, 150 mm, and 200 mm. - A coating process according to
FIG. 2 may be preprogrammed, or programmed on the fly to adjust parameters such as number of coats, or passes with the sprayer between drying steps, number of cycles of spraying and drying, etc. These and related parameters may be governed by the polymer-drug or solvent used, type of stent or medical device being coated, e.g., surface geometry. In particular embodiments the protocol for coating a stent may be governed by a predetermined number of coating cycles, i.e., spraying then drying, based on an analytically determined final coating weight, or by intermittent weighing of the stent to determine the number of cycles needed to arrive at the target coating weight. -
FIGS. 3 and 4 show an assembled rear perspective view and exploded front perspective assembly view, respectively, of thedryer 10. A mouth or exit of thedryer 10 is present at the base of the dryingchamber 32 and has dimensions the same as the opening to the dryingchamber 32; in other words, the walls forming the dryingchamber 32 are parallel to each other or the cross-sectional area of the entrance to the dryingchamber 32 is the same as the cross-sectional area of the opening through which the stent passes when entering/exiting the dryingchamber 32. A gas supply is connected to an entrance of thedryer 10 provided by thebase housing 20. The drying gas, e.g., heated nitrogen or air, is supplied through agas supply 2 b connected to aheater assembly 2. Theheater assembly 2 includes a tubular conduit with heating coils exposed to the gas stream as it travels towards the dryer entrance 9. The coils are connected to a power source via a power connection. - A plenum of the
dryer 10 is formed by internal volumes of thebase housing 20, thediffuser housing 30 and abase cap 70. Perspective views of thebase cap 70 anddiffuser housing 30 are illustrated inFIGS. 5 and 6 , respectively. A hole in the dryer base housing 20 (hidden from view) is formed to co-align with a similar shaped hole in the base cap 70 (also hidden from view) to provide a passage for gas into the interior of thebase cap 70. The hole or passage for gas through thebase housing 20 includes a threading to sealingly engage a complimentary threaded fitting 2 c of the heated gas supply. Gas entering through this passage passes directly into the interior of thebase cap 70, exits through ahole 72 formed at the top of thebase cap 70 then passes up through thediffuser housing 30. Thebase cap 70 anddiffuser housing 30 are contained within thebase housing 20 when fully assembled. - To account for any thermal energy loss for gas near the walls of the
housings diffuser housing 30 so that the gas entering the dryingchamber 32 has a more uniform heat transfer across the length of the stent. Preferably three mixing regions are used fordryer 10. Each mixing region is formed by adiffuser screen 42 andspacer 40. Each screen and spacer are stacked on top of each other, as indicated inFIG. 4 . From tests it was found that three spacers and screen assemblies were sufficient to cause no more than about a 1 degree Celsius temperature difference within the dryingchamber 32 during a drying step. -
FIG. 4 indicates the order of assembly of the portions forming the plenum of thedryer 10, i.e.,diffuser housing 30,base cap 70,base housing 20 and spacers and screens 40, 42. The three spacers and screens 40, 42 are placed inserted within thediffuser housing 30 and may be held in place by pins at theedge 31. Thediffuser housing 30 is placed within thedryer base 20 through abottom edge 24 thereof. Thedryer housing 20 anddiffuser housing 30 are then placed on thebase cap 70 such that alower edge 24 of thedryer housing 20 rests on alower flange 76 of thebase cap 70. The lower spacer 40 a rests on anupper surface 74 of thebase cap 70. Thebase housing 20 is press-fit onto thebase cap 70 to provide a fluid-tight seal between the walls of the two structures. This assembled configuration of thedryer 10 is depicted inFIG. 1A . - As mentioned above, gas travels from the gas supply into the interior of the
base cap 70, though theexit hole 72 and then through thediffuser housing 30. When thediffuser housing 30 is lifted up to position the stent within the drying chamber 32 (FIG. 1B ), the spacer 40 a lifts off thesurface 74 of thebase cap 70. To ensure gas passes directly from the base cap into thediffuser housing 30, a tight but slidable fit is formed between the interior walls of thehousing 20 and alower flange 31 of thediffuser housing 30. In essence, this fit maintains a desired gas pressure within the plenum while thedryer 10 is expanded (orhousing 30 lifted) to receive the stent in the dryingchamber 32, and while allowing thediffuser housing 30 to be moved up and down by theactuator 50 while thehousing 20 andbase cap 70 remain stationary (FIG. 1B ). The travel upwards of thediffuser housing 30 within thebase housing 20 is limited by theflange 31. After thediffuser housing 30 has traveled a sufficient distance (to place the stent within the drying chamber 32) theflange 31 abuts an upper surface of theopening 22 of thediffuser housing 20, thereby preventing further upward movement. To promote the seal between the interior walls of thehousings edge 31 slides against along the walls of thehousing 20 as thediffuser housing 30 is being moved upwards and downwards within thehousing 20 by theactuator 50. More generally, the sliding fit between these telescoping parts enables a plenum pressure to be achieved and maintained (no leaks) while thedryer 10 is retracted/shortened and expanded/lengthened. - As just alluded to, the aforementioned structure, i.e.,
housings base cap 70, andmechanism 50 that form the plenum for thedryer 10 may be thought of as a telescoping dryer. Prior to the stent being positioned over the dryingchamber 32, thediffuser housing 30 is retracted within thebase housing 20 to provide clearance for the stent andmandrel 15 to be linear displaced from the spray station to a position over the dryingchamber 32. The dryer plenum is then essentially elongated or expanded to bring the stent into the dryingchamber 32 of thediffuser housing 30. Thus, a “telescoping dryer assembly” is intended to mean an arrangement of housings forming a plenum that slide inward and outward in overlapping fashion in a manner analogous to how a hand telescope slides inward and outward in an overlapping fashion, to thereby provide a variable length channel or internal passage for a pressurized fluid to pass through, i.e., a variable length plenum. - Referring to
FIGS. 3 and 4 , thedryer 10 components andactuating mechanisms blocks 16 andbrackets 12. Theactuating mechanism 55 is used to displace left andright grippers distal end 15 a of themandrel 15; this movement being indicated by the left and right arrows G inFIG. 3 . A detailed view of eachgripper FIGS. 7A-7B . - The actuating mechanism 50 (e.g., one or more hydraulic actuators, such as air cylinders, operated as part of a servomechanism pre-programmed or controlled by a computer processor to produce the desired movement in the
housing 30 in accordance with a drying/spraying process as shown inFIG. 2 ) is used to raise and lower thediffuser housing 30; this movement indicated by the up and down arrows L inFIG. 3 . A connectingplate 54 has a rim, which is placed over the diffusing housing and secured to atop ledge 34 of thediffuser housing 30, and aflange 54 a that is secured to aplatform 54 b that is movable up and down by a pair ofair cylinders plate 54 to pull up on thehousing 30 when the plenum is being extended or lengthened (FIGS. 1B and 3 ), and push down on thehousing 30 when the plenum is being retracted or shortened (FIG. 1A ).FIG. 3 shows thedryer 10 configuration with thehousing 30 raised to position the stent within the dryingchamber 32 and thegripper pair end 15 a of themandrel 15. This is also the configuration shown inFIG. 1B . -
FIG. 5 shows a perspective view of thebase cap 70, with the portions identified as previously described. As can be appreciated by comparing the contours of the base captop surface 74 and the housing 30 (FIG. 6 ), thedryer 10 preferably has an elongate shape with rounded ends, just as the dryingchamber 32 is shaped to receive the stent or scaffold. Thebase cap 70 may be formed to have walls that are thicker than thehousings 20, 30 (seeFIG. 1A ) to provide increased insulation capability. Since the gas enters here and is redirected 90 degrees to exit fromhole 72, there is a greater heat loss possibility than after the gas exits throughhole 72. As such, the walls are made thicker and preferably they are made from PEEK. As described earlier, a last step of the assembly fordryer 10 is to press fit the housing 20 (withdiffuser housing 30 inside) onto thebase cap 70. This last step essentially seals thedyer 10 and forms the interior space for the dryer plenum. -
FIG. 6 shows a perspective view of thediffuser housing 30, with features of this structure as previously described. The dryingchamber 32 is elongate with rounded ends to receive the stent or scaffold therein. The dryingchamber 32 provides a surrounding shield orwalls 30 b that rise up from theledge 34, whichledge 34 locates the exit opening from the plenum (the dryer mouth) into the dryingchamber 32, thereby also reflecting a depth of the dryingchamber 32. Gas flowing near the stent and within the dryingchamber 32 may exit from the plenum at a relatively low velocity which favorably limits the amount of regress or interference from ambient air. As mentioned earlier, by providing a shield and gas at a lower exit velocity which maintains its heat when exposed to the stent, there is an alternative to the dryer assemblies described in US20110059228 and US20110000427. The mouth of the dryer is located at the base of the drying chamber. The opening provided for the stent is about the same size as the mouth size (not shown in the drawings). -
FIGS. 7A and 7B show perspective views ofgrippers arms grippers FIG. 4 ) using bolts. At the head of thegrippers complimentary slots distal end 15 a of themandrel 15 within a circular passage formed when theslots FIG. 2 ). V-shapedsections slots mandrel 15 into thesemicircular slots FIGS. 1B and 3 ). As can be appreciated by inspecting the spacing between the V-shapedsection 66 and slot 63 a ofgripper 62, the closer spacing between the V-shapedsection 67 andslot 63 b of thegripper 64, the dimension G1 inFIGS. 7A-7B , and the interlocking manner in which the grippers engage the mandrel, as shown inFIG. 3 , the V-shapedsection 67 is disposed within thespace 69 of thegripper 62 when the mandrel end 15 a is engaged by thegrippers chamber 32, thegrippers slots grippers slots chamber 32 and held in position when the drying gas is passed over the stent. Themandrel end 15 a may rotate while it is disposed within the circular passage formed by theslots - The
shield 30 b forming the dryingchamber 32 includes afirst notch 36 disposed at one rounded end, and asecond notch 38 disposed at a second or opposed rounded end. Thesenotches chamber 32 during the drying. When the gas exits, even at a low velocity the stent will oscillate since it rotates which presents a varying surface area to the gas exiting (in addition to the non-laminar or transient flow in and around the stent). The problem of oscillations is especially noted for stents that are 40 mm and longer, e.g., stents (or scaffolds) intended for the superficial femoral artery. To meet these needs thedryer 10 includes a support for themandrel 15distal end 15 a, i.e.,mandrel grippers 60, in addition to thenotches grippers 60 the stent becomes effectively fixed-supported at the mandreldistal end 15 a when disposed over the dryer mouth (exit of the plenum), yet is still capable of being rotated about the mandrel axis by a rotary mechanism coupled to the mandrel. This support may be achieved without interference with drying and prevents contact between the stent/scaffold and thewalls 30 b ormandrel 15 as the gas passes over the stent/scaffold. - The stent is mounted onto the
mandrel 15 prior to the start of the stent coating process (FIG. 2 ). Themandrel 15 controls the stent position during drying and spraying. Themandrel 15 generally maintains axial alignment of the stent, and causes the stent to rotate at generally the same rate as themandrel 15, which has a proximal end that fits into a chuck. The chuck delivers a torque to themandrel 15. Theslots mandrel 15 to rotate. The matedgrooves FIGS. 7A-7B ) also provide this clearance for rotation. Some heating gas will escape through theslots -
FIG. 8 shows a perspective view of thebase housing 20, with the portions identified as previously described. As mentioned earlier, thebase housing 20 includes a threaded fitting (hidden from view) that receives the fitting for the gas supply. Thediffuser housing 30 and spacers/screens 40, 42 are received in thebase housing 20. The walls forming the dryingchamber 32 extend out from theopening 22 of the base housing 20 (seeFIG. 1B ). - For the drying systems described in US20110059228 and US20110000427 there is preferably an oven step for removing residual solvent from the stent or scaffold. In an additional aspect of disclosure, the oven step may be skipped as tests show that the
dryer 10 and process as shown and described may remove solvent at a sufficient rate during the process ofFIG. 2 to obviate an oven step. This is desirable as it reduces manufacturing time for the medical device. - Twelve as-coated samples were collected to assess efficiency of the
dryer 10 with and without a later oven step. Those samples were processed using inter pass dry temperature at 50 C. Those samples were divided into two groups—Group A and Group B. The six group A samples were kept in a tightly sealed vial and in the refrigerator prior to residual solvent testing, and while the six group B samples proceeded with an additional oven dry at 50 C for 30 minutes immediately after the final coating step, then kept in the vial. - The residual acetone data for the two groups are listed in the TABLE 1. The data shows that there is not much different between the average of the residual acetone level between the two groups (between 1 to 2 micrograms). This is because the actual amount of a residual solvent present in a coated stent can vary within a few micro-grams of a measured amount, which is what TABLE 1 shows. Moreover, in some applications up to 5 μg of residual solvent remaining in the coating is considered acceptable. Accordingly, the test suggests there may be no need to have an oven bake step when using a dryer constructed in accordance with
dryer 10. -
TABLE 1 residual acetone levels for Groups A vs. Group B (six 12 mm stents) Residual acetone μg/stent (12 mm) Group A Group B 100165795 100165796 Stent # without oven step with Oven step 1 1.17 1.66 2 1.06 1.29 3 1.06 1.48 4 0.88 1.37 5 5.20* (outlier) 1.04 6 1.14 1.04 Average 1.0 (does not include the outlier) or 1.8 1.3 (includes the outlier) - A gas flow rate through the
heater assembly 2 inFIG. 1 may be monitored/controlled by a commercially available mass flow regulator (not shown). For example, such a mass flow regulator may be used to operate an adjustable valve coupling thegas supply line 2 b to a gas source to produce the desired flow rate. One example of a suitable mass flow regulator is the Aalborg GFCS series programmable mass flow regulator. A use of a mass flow regulator and related control system suitable for use with aspects of the disclosure is described in U.S. application Ser. No. 12/540,302. - During a coating process, the dryer is not in use when the stent is being coated. If the dryer is shut down or the flow rate reduced the temperature of the gas at the entrance to the
plenum 10 of the dryer 1 will decrease. If the stent is moved into position above the nozzle mouth for drying and the valve opened to increase the flow rate, there will be a period of transient flow. It is desirable to avoid a period of solvent removal by transient gas flow, since the rate or amount of solvent removal by transient flow can be difficult to predict. It is preferred, therefore, that the stent is dried only during steady state flow conditions. - If gas flow at the dryer is instead maintained at a constant rate, then the temperature may be maintained. However, this wastes gas resources. It would be desirable if the gas flow rate could be reduced when the dryer is not in use while holding the gas temperature at a constant value.
- To meet this need, a closed loop control is preferably implemented with a stent dryer system according to the disclosure, so that the gas temperature may be maintained at variable flow rates. Referring to
FIG. 9 , a schematic of this closed-loop control is illustrated. Acontroller 300 continuously receives input temperatures at the entrance of the plenum from athermocouple 302 and the gas flow rate upstream of the plenum entrance from aflow sensor 304. Thecontroller 300 may be programmed to reduce the gas flow rate when the dryer is not in use, and increase the gas flow rate when the stent is ready to be moved into position above the dryer mouth. - As the flow rate is adjusted by opening/closing the
adjustable valve 308, the controller senses a change in temperature from input received at thethermocouple 302, at which point it will increase/decrease the power delivered to the heating coils by affectingcontrol 306 for power so that the temperature remains constant, regardless of the actual flow rate. Thus, according to this aspect of the disclosure, a dryer system may be operated at variable flow rates during a coating process while maintaining a substantially steady state gas flow during the drying stage, or a minimal period of transient flow conditions until a steady state condition is reached. This improves/maintains the predictability of solvent removal during drying, minimizes down time and allows gas resources to be conserved. The coated stent is almost immediately subject to the drying step and dried in a manner that allows the improved prediction of solvent removal. As discussed earlier, this is a critical step in the process of producing a predictable release rate for a drug-eluting stent and accurate assessment of whether the desired drug-polymer coating weight has been reached. - After, or just prior to completion of an application of coating composition on the stent, the
controller 300 increases the gas flow temperature to the drying gas flow rate. While the gas flow is being increased, thecontroller 300 monitors the temperature at theplenum entrance 2 c by input received from thethermocouple 302 and the power increased to the heating coils as necessary to maintain the temperature of the exiting gas flow. Once the gas flow has reached the operating flow rate and temperature, the stent is moved into position above the dryingchamber 32 and thehousing 30 raised. The stent is rotated. After drying is complete, the gas flow is again returned to the idle state and the power to the heating coils decreased as necessary to maintain the same gas flow temperature (based on input received from the thermocouple 302) at/nearlocation 2 c. The process repeats until the desired coating weight is obtained. - The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
- These modifications can be made to the invention in light of the above detailed description. The terms used in claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by claims, which are to be construed in accordance with established doctrines of claim interpretation.
Claims (23)
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US13/235,238 US9909807B2 (en) | 2011-09-16 | 2011-09-16 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
EP12750956.0A EP2756247B1 (en) | 2011-09-16 | 2012-08-14 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
JP2014530670A JP6256920B2 (en) | 2011-09-16 | 2012-08-14 | Dryer for removing solvents from drug-eluting coatings on medical devices |
EP18154935.3A EP3382309A1 (en) | 2011-09-16 | 2012-08-14 | Method of spraying a composition on a stent followed by a drying step |
PCT/US2012/050803 WO2013039637A1 (en) | 2011-09-16 | 2012-08-14 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
US15/874,772 US20180142952A1 (en) | 2011-09-16 | 2018-01-18 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
Applications Claiming Priority (1)
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US13/235,238 US9909807B2 (en) | 2011-09-16 | 2011-09-16 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
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US15/874,772 Division US20180142952A1 (en) | 2011-09-16 | 2018-01-18 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
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US20130071549A1 true US20130071549A1 (en) | 2013-03-21 |
US9909807B2 US9909807B2 (en) | 2018-03-06 |
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US13/235,238 Expired - Fee Related US9909807B2 (en) | 2011-09-16 | 2011-09-16 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
US15/874,772 Abandoned US20180142952A1 (en) | 2011-09-16 | 2018-01-18 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
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US15/874,772 Abandoned US20180142952A1 (en) | 2011-09-16 | 2018-01-18 | Dryers for removing solvent from a drug-eluting coating applied to medical devices |
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US (2) | US9909807B2 (en) |
EP (2) | EP3382309A1 (en) |
JP (1) | JP6256920B2 (en) |
WO (1) | WO2013039637A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9724718B2 (en) | 2011-10-13 | 2017-08-08 | Abbott Cardiovascular Systems Inc. | Adjustable support for tubular medical device processing |
US9795497B2 (en) | 2014-09-18 | 2017-10-24 | Abbott Cardiovascular Systems Inc. | Thermal processing of polymer scaffolds |
US9931787B2 (en) | 2014-09-18 | 2018-04-03 | Abbott Cardiovascular Systems Inc. | Crimping polymer scaffolds |
US10010653B2 (en) | 2016-02-05 | 2018-07-03 | Abbott Cardiovascular Systems Inc. | Methods for increasing coating strength to improve scaffold crimping yield |
US10184719B2 (en) * | 2015-04-09 | 2019-01-22 | Boston Scientific Scimed, Inc. | Coated medical devices and methods for drying coated medical devices |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9724219B2 (en) | 2012-10-04 | 2017-08-08 | Abbott Cardiovascular Systems Inc. | Method of uniform crimping and expansion of medical devices |
CN104056764B (en) * | 2014-06-30 | 2015-08-05 | 安徽晶皓电子科技有限公司 | Bubble machine baked by fluorescent lamp |
US10660773B2 (en) | 2017-02-14 | 2020-05-26 | Abbott Cardiovascular Systems Inc. | Crimping methods for thin-walled scaffolds |
US10555825B2 (en) | 2017-11-09 | 2020-02-11 | Abbott Cardiovascular Systems Inc. | Rotation of a medical device during crimping |
US10967556B2 (en) | 2018-06-11 | 2021-04-06 | Abbott Cardiovascular Systems Inc. | Uniform expansion of thin-walled scaffolds |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3023515A (en) * | 1959-04-13 | 1962-03-06 | Stern Harriet Jean | Portable hair dryer |
US3814111A (en) * | 1972-12-26 | 1974-06-04 | Schick Inc | Portable hooded hair moisturizer and dryer |
US20030099765A1 (en) * | 2001-11-26 | 2003-05-29 | Swaminathan Jayaraman | Process for coating a surface of a stent |
US20030215564A1 (en) * | 2001-01-18 | 2003-11-20 | Heller Phillip F. | Method and apparatus for coating an endoprosthesis |
US7211150B1 (en) * | 2002-12-09 | 2007-05-01 | Advanced Cardiovascular Systems, Inc. | Apparatus and method for coating and drying multiple stents |
US20070275175A1 (en) * | 2002-03-15 | 2007-11-29 | Hossainy Syed F | Apparatus and method for coating stents |
US20080307668A1 (en) * | 2007-06-15 | 2008-12-18 | Sidney Watterodt | Methods and devices for drying coated stents |
US20100070026A1 (en) * | 2008-09-12 | 2010-03-18 | Fujifilm Corporation | Stent with porous membrane and manufacturing method thereof |
US20110059228A1 (en) * | 2009-09-04 | 2011-03-10 | Abbott Cardiovascular Systems Inc. | Drug-Eluting Coatings Applied To Medical Devices By Spraying And Drying To Remove Solvent |
Family Cites Families (31)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2794708A (en) | 1954-03-15 | 1957-06-04 | Hermann C Starck Ag | Method for the production of a substantially pure boron |
FR1238899A (en) | 1959-07-09 | 1960-08-19 | Ameliorair Sa | Improvements made to dryers for gas-permeable sheet products, in particular for sheet yarn |
GB1024671A (en) | 1962-05-30 | 1966-03-30 | Bristol Fan Company Ltd | Drying nozzle |
DE2253170C2 (en) | 1972-10-30 | 1988-12-22 | Hoechst Ag, 6230 Frankfurt | Method and device for treating a freely floating material web |
JPS60172713A (en) * | 1984-02-17 | 1985-09-06 | Hitachi Ltd | Fluid flow passage |
US4733665C2 (en) | 1985-11-07 | 2002-01-29 | Expandable Grafts Partnership | Expandable intraluminal graft and method and apparatus for implanting an expandable intraluminal graft |
US4800882A (en) | 1987-03-13 | 1989-01-31 | Cook Incorporated | Endovascular stent and delivery system |
US4886062A (en) | 1987-10-19 | 1989-12-12 | Medtronic, Inc. | Intravascular radially expandable stent and method of implant |
US5070627A (en) | 1990-01-16 | 1991-12-10 | W. R. Grace & Co.-Conn. | Directional diffusion nozzle air bar |
CA2060067A1 (en) | 1991-01-28 | 1992-07-29 | Lilip Lau | Stent delivery system |
CA2380683C (en) | 1991-10-28 | 2006-08-08 | Advanced Cardiovascular Systems, Inc. | Expandable stents and method for making same |
JPH06115410A (en) * | 1992-10-05 | 1994-04-26 | Takeuchi Iron Works Corp | Body drying equipment for vehicle |
JP2703510B2 (en) | 1993-12-28 | 1998-01-26 | アドヴァンスド カーディオヴァスキュラー システムズ インコーポレーテッド | Expandable stent and method of manufacturing the same |
US6018886A (en) | 1996-06-25 | 2000-02-01 | Eastman Kodak Company | Effect of air baffle design on mottle in solvent coatings |
US5906862A (en) | 1997-04-02 | 1999-05-25 | Minnesota Mining And Manufacturing Company | Apparatus and method for drying a coating on a substrate |
US7504125B1 (en) * | 2001-04-27 | 2009-03-17 | Advanced Cardiovascular Systems, Inc. | System and method for coating implantable devices |
GB0129740D0 (en) | 2001-12-12 | 2002-01-30 | Falmer Investment Ltd | Improvements in and relating to processing fabric |
US6702101B2 (en) | 2001-12-21 | 2004-03-09 | Spraying Systems Co. | Blower operated airknife with air augmenting shroud |
US6785982B2 (en) | 2002-06-07 | 2004-09-07 | Eastman Kodak Company | Drying apparatus and method for drying coated webs |
US7074276B1 (en) | 2002-12-12 | 2006-07-11 | Advanced Cardiovascular Systems, Inc. | Clamp mandrel fixture and a method of using the same to minimize coating defects |
JP4406901B2 (en) * | 2003-07-03 | 2010-02-03 | 株式会社山武 | Fluid rectifier |
US7892592B1 (en) * | 2004-11-30 | 2011-02-22 | Advanced Cardiovascular Systems, Inc. | Coating abluminal surfaces of stents and other implantable medical devices |
US8945598B2 (en) | 2005-12-29 | 2015-02-03 | Cordis Corporation | Low temperature drying methods for forming drug-containing polymeric compositions |
US7340846B1 (en) | 2007-03-23 | 2008-03-11 | Wuu-Cheau Jou | Drying gun |
WO2008156920A2 (en) * | 2007-06-15 | 2008-12-24 | Abbott Cardiovascular Systems Inc. | System and method for coating a stent |
US7897195B2 (en) | 2007-06-15 | 2011-03-01 | Abbott Cardiovascular Systems Inc. | Devices for coating stents |
US8367150B2 (en) | 2007-06-15 | 2013-02-05 | Abbott Cardiovascular Systems Inc. | Methods and apparatus for coating stents |
US8505213B2 (en) | 2009-04-30 | 2013-08-13 | Motor City Wash Works, Inc. | Extendable nozzle for a vehicle drying apparatus |
US8795761B2 (en) | 2009-07-02 | 2014-08-05 | Abbott Cardiovascular Systems Inc. | Removing a solvent from a drug-eluting coating |
US8567340B2 (en) | 2009-08-12 | 2013-10-29 | Abbott Cardiovascular Systems Inc. | System and method for coating a medical device |
US8573148B2 (en) | 2009-09-04 | 2013-11-05 | Abbott Cardiovascular Systems Inc. | System for coating a stent |
-
2011
- 2011-09-16 US US13/235,238 patent/US9909807B2/en not_active Expired - Fee Related
-
2012
- 2012-08-14 JP JP2014530670A patent/JP6256920B2/en not_active Expired - Fee Related
- 2012-08-14 EP EP18154935.3A patent/EP3382309A1/en not_active Withdrawn
- 2012-08-14 EP EP12750956.0A patent/EP2756247B1/en not_active Not-in-force
- 2012-08-14 WO PCT/US2012/050803 patent/WO2013039637A1/en active Application Filing
-
2018
- 2018-01-18 US US15/874,772 patent/US20180142952A1/en not_active Abandoned
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3023515A (en) * | 1959-04-13 | 1962-03-06 | Stern Harriet Jean | Portable hair dryer |
US3814111A (en) * | 1972-12-26 | 1974-06-04 | Schick Inc | Portable hooded hair moisturizer and dryer |
US20030215564A1 (en) * | 2001-01-18 | 2003-11-20 | Heller Phillip F. | Method and apparatus for coating an endoprosthesis |
US20030099765A1 (en) * | 2001-11-26 | 2003-05-29 | Swaminathan Jayaraman | Process for coating a surface of a stent |
US20070275175A1 (en) * | 2002-03-15 | 2007-11-29 | Hossainy Syed F | Apparatus and method for coating stents |
US7211150B1 (en) * | 2002-12-09 | 2007-05-01 | Advanced Cardiovascular Systems, Inc. | Apparatus and method for coating and drying multiple stents |
US20080307668A1 (en) * | 2007-06-15 | 2008-12-18 | Sidney Watterodt | Methods and devices for drying coated stents |
US20100070026A1 (en) * | 2008-09-12 | 2010-03-18 | Fujifilm Corporation | Stent with porous membrane and manufacturing method thereof |
US20110059228A1 (en) * | 2009-09-04 | 2011-03-10 | Abbott Cardiovascular Systems Inc. | Drug-Eluting Coatings Applied To Medical Devices By Spraying And Drying To Remove Solvent |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9724718B2 (en) | 2011-10-13 | 2017-08-08 | Abbott Cardiovascular Systems Inc. | Adjustable support for tubular medical device processing |
US9724717B2 (en) | 2011-10-13 | 2017-08-08 | Abbott Cardiovascular Systems Inc. | Adjustable support for tubular medical device processing |
US9795497B2 (en) | 2014-09-18 | 2017-10-24 | Abbott Cardiovascular Systems Inc. | Thermal processing of polymer scaffolds |
US9931787B2 (en) | 2014-09-18 | 2018-04-03 | Abbott Cardiovascular Systems Inc. | Crimping polymer scaffolds |
US10278844B2 (en) | 2014-09-18 | 2019-05-07 | Abbott Cardiovascular Systems Inc. | Thermal processing of polymer scaffolds |
US10184719B2 (en) * | 2015-04-09 | 2019-01-22 | Boston Scientific Scimed, Inc. | Coated medical devices and methods for drying coated medical devices |
US20190137177A1 (en) * | 2015-04-09 | 2019-05-09 | Boston Scientific Scimed, Inc. | Coated medical devices and methods for drying coated medical devices |
US10921056B2 (en) * | 2015-04-09 | 2021-02-16 | Boston Scientific Scimed, Inc. | Coated medical devices and methods for drying coated medical devices |
US10010653B2 (en) | 2016-02-05 | 2018-07-03 | Abbott Cardiovascular Systems Inc. | Methods for increasing coating strength to improve scaffold crimping yield |
Also Published As
Publication number | Publication date |
---|---|
EP2756247B1 (en) | 2018-03-21 |
JP6256920B2 (en) | 2018-01-10 |
US20180142952A1 (en) | 2018-05-24 |
EP3382309A1 (en) | 2018-10-03 |
EP2756247A1 (en) | 2014-07-23 |
JP2015500972A (en) | 2015-01-08 |
US9909807B2 (en) | 2018-03-06 |
WO2013039637A1 (en) | 2013-03-21 |
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